Lenses, both glass and plastic, and semiconductor wafers are polished before use. Polishing is generally accomplished by bringing the workpiece into rubbing contact with a pad while circulating a slurry of finely divided abrasive particles in an acqueous medium into the area of contact between the pad and the workpiece. The slurry drains from the workpiece surface into a sump from which it is recirculated to further contact with the workpiece by a pump.
Polishing slurries commonly encounter three problems in greater or lesser degree. One problem is the tendency of the solid particles of the slurry to settle rapidly especially when the polishing action is interrupted with the result that the settled material must be redispersed before its use in polishing can be continued. A second problem is that polishing slurries commonly have little capacity to hold the debris removed by the workpiece during polishing action in suspension with the result that the useful life of the polishing slurry is short. A third problem is the tendency of polishing slurries to foam during the course of use with the result that recirculation by a pump is inefficient and even impossible in serious foaming situations.
It is the object of this invention to provide a polishing slurry which is stable, has a long useful life and is essentially foam free during recirculation in a normal polishing operation.